Absorption, attenuation, and grids Flashcards Preview

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Flashcards in Absorption, attenuation, and grids Deck (23)
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1
Q

PEA results in complete

A

x-ray absorption

2
Q

compton causes

A

scatter

3
Q

attenuation

A

some penetrating x-rays are absorbed by tissues

4
Q

exponential attentuation

A

absorption depends on tissues thickness

5
Q

HVL measures x-ray

A

quality/penetrability

6
Q

HVL

A

thickness of absorbing material needed to reduce x-ray intensity by half

7
Q

types of filtering

A
  1. tungsten anode
  2. x-ray tube housing
  3. added filtration
8
Q

exposing body parts with unequal thickness

A

compensatory filter

9
Q

primary bean attenuated by 90%

A

tenth value layer (TVL)

10
Q

scatter intensity depends on..

A

kVp, beam field size, and patients thickness

11
Q

grid is a series of

A

lead strips –> cleans up scatter (up to 80%)

12
Q

grid ratio

A

R=h/D

13
Q

most frequent grid ratio used

A

8:1 to 10:1

14
Q

higher ratio grids

A

less scatter but more radiation exposure is needed

15
Q

paralleled grid flaw

A

grid cut-of artefact

16
Q

grid cut-off

A

undesirable absorption of primary x-rays

17
Q

grid cut-off is inversely related to

A

source image distance (SID)

18
Q

disadvantages of moving grids

A

bulky mechanism and blurring effect

19
Q

stationary grids mostly used for

A

portable radio and upright horizontal views

20
Q

higher grid ratio can be met by

A

increase in mAs

21
Q

mAs should be increased

A

10% for each cm of air-gap

22
Q

commonly obtained using air-gap technique

A

lateral cervical

23
Q

used with out grid to reduce scatter and maintain contrast

A

air-gap technique